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  • Author or Editor: R. Gallé x
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Natural habitat edges are known to influence the vegetation structure, the microclimate and thereby the invertebrate assemblages. We studied the spiders of two forest edges in the forest-steppe zone of the Great Hungarian Plain (Site 1: a dense juniper shrub — open grassland and Site 2: a juniper and poplar forest — open grassland edge, respectively). The spider assemblages were sampled with pitfall traps arranged in 5 × 20 grid at the habitat edges. Observed and estimated species richness was higher for the grasslands than for the forests. Renyi’s diversity ordering was applied to compare species diversity. The results showed that the grasslands were more diverse in terms of spider species than the forests. The composition of spider assemblages was significantly different between the two habitat types. At Site 2, a higher number forest specialists penetrated into the grassland. Presumably this was due to the shading effect of the nearby poplar trees. Constrained ordinations also revealed a strong influence of the neighbouring poplar trees and vegetation structure on the spider assemblages. No exclusively edge associated species were found on either of the two sharp forest edges.

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Abstract

We briefly complement Endrédi et al. (2019) forum paper from terrestrial animal ecological points of view. We discuss the origins of trait-based approach, challenges of trait classifications, and we provide an example of a commonly used trait, body size.

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Significant proportion of crop lands have been abandoned as management strategies have changed in Central and Eastern Europe in the past decades. The study of insect versus plant communities in such areas could help us understand how these processes take place, and whether these communities return to a semi-natural state maintained by human activities. Amongst insects ants, as ecosystem engineers, are a perfect target group in this respect. We studied epigaeic ant and plant communities of abandoned old-fields in Romania. Contrary to our expectations, the total number of ant species did not increase with time during succession on old-fields contrary to plants, where an increase was registered in the total number. Disturbancetolerant ant species dominated the ant communities throughout the successional gradient, while in the case of plants a transition was found from weed-dominated to semi-natural communities. The diversity of both ant and plant communities increased after the 1-year stage, but the patterns were different. While a return to semi-natural state could be observed in plants during old-field succession, such a definite change did not occur in ants. This might be caused by the landscape context: the lack of connectivity of old-fields to larger natural areas. While plant propagules of semi-natural and natural habitat species can still successfully colonize the old fields even under such conditions, ant colonizers are mainly disturbance-tolerant species typical for agricultural areas, which can be hardly replaced by typical grassland species. Our findings underline the existence of important discrepancies between plant and ant community succession, mostly treated as paralleling each other. This is the first study to handle the effect of abandonment on ant and plant communities simultaneously in Eastern Europe.

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Habitat boundaries in general and forest edges in particular belong to the central issues in ecology. Theories about community and environmental edge-responses are diverse, but there is a lack of sufficient supporting field evidence: no consensus exists about distinctness and diversity of edges, and the existence of edge-related species. Moreover, as most studies focus on man-made edges, natural forest edges are less understood. We studied xeric forest edges in a wooded-steppe area. Twelve forest patches were selected, and plots were set up within the edges, the forest interiors and the grasslands. Species composition, species richness and Shannon diversity were compared between the three habitat types as well as between differently oriented edges. We identified diagnostic species for all habitats. Local habitat preferences of the edge-related species were compared to their regional preferences. Environmental factors of the different habitats were assessed by using ecological indicator values. Forest edges differed both from forest interiors and grasslands, forming a narrow but distinct habitat type between them. Species composition of the edges was not simply a mixture of forest and grassland species, but there were several edge-related species, most of which are regionally regarded as typical of closed steppe grasslands. Neither shady conditions of the forests, nor dry conditions of the grasslands are tolerated by these species; this is why they are confined to edges. Species richness and Shannon-diversity were higher within edges than in either of the habitat interiors. Ecological indicator values suggested that light intensity and temperature were higher in the edges than in the forests, but were lower than in the grasslands. In contrast, soil moisture was lower in the edges than in the forests but was higher than in the grasslands. There were slight differences between differently exposed edges concerning species composition, species richness and Shannon diversity. We conclude that edges should be considered an integral part of wooded-steppes. Their high diversity may have nature conservation implications. Our study emphasizes that edge species may be confined to edges only locally, but may have a broader distributional range in other areas. These species may be referred to as local edge species. Our results also point out that the very same edge can be interactive and non-interactive at the same time, depending on the characteristics considered.

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